The typical vehicle parking brake control mechanism has either a hand-pulled or a foot-pushed apply lever which upon movement in a parking brake apply direction by a vehicle operator arcuately rotates a drum or pulley or similar structure, or the opposite end of the apply lever, to which one end of a parking brake cable is attached, exerting tension force through the cable to a brake mechanism located somewhere in the vehicle drive line between the vehicle engine and the vehicle drive wheels. Usually, the vehicle brake mechanism is located at the vehicle wheels on one axle location such as the rear axle. In any case, the tension force in the cable will apply one or more brakes in a parking mode. When applied, the parking brakes strongly resist or prevent movement of the vehicle while it is stopped.
Such vehicle parking brake control mechanisms also have arrangements whereby the brake parking brake cable is held in tension after the hand or foot applied force is removed. These arrangements typically latch or lock the drum or the parking brake lever in position, so that the resistance or reaction force maintaining the brake apply tension force path from the parking brake cable to a fixed part of the vehicle passes from the parking brake cable through the drum to a part of the parking brake operating lever. The drum or the part of the parking brake operating lever acting as such is typically mounted on a pivot shaft or bushing which is mounted on a bracket provided for that purpose, the bracket being operatively fixed to the frame or body of the vehicle.
The latching or locking mechanism of the typical parking brake control mechanism may be any of several basic designs. For example, a toothed gear or gear sector, operatively mounted on or even a part of the drum or the parking brake lever, may be selectively engaged by a toothed pawl which is pivotally or linearly movable into engagement with one or more teeth of the gear or gear sector so as to prevent releasing-direction rotational movement of the drum or the parking brake lever. With the pawl being operatively pivotally mounted on the earlier mentioned mounting bracket, the parking brake force path is transmitted from the gear or gear sector to the vehicle frame or body. In another example, the drum may be latched in the brake-applied position by a spring clutch.
The pawl or the spring clutch is typically released by a hand-operated arrangement which when pulled or pushed causes the pawl or the spring clutch to be moved so as to terminate the latched brake-applied position, relieving the tension in the parking brake cable and permitting the brake or brakes which were applied through it to be released.
The following U.S. Patents are typical of previously known parking brake apply and release mechanisms of the types commonly used on vehicles either currently or at some time in the past, or at least proposed for such use. Some of the patents noted below, while not in such parking brake control mechanisms, have structural features of general interest in developing a fuller understanding of the background of the invention herein disclosed and claimed.
U.S. Pat. No. 210,442--Whipple, patented Dec. 3, 1878, is of interest because it is an early disclosure of a brake operator using a rack and pinion gear for locking the brake in the set position and for releasing the brake. The brake rod which operates the wagon brake is attached directly to the hand operated lever on which the pinion gear is mounted. The pinion gear provides an automatic locking device on the hand operated lever which engages the rack in locking relation when the brake is set by moving the hand operated lever in one pivotal direction. This engagement is terminated by moving the hand operated lever in its disengaging direction, causing the pinion gear to be disengaged from its locking position in relation to the rack and allowing the hand operated lever and the brake rod to be moved to release the wagon brake.
U.S. Pat. No. 1,968,159--Nickliss, patented Jul. 31, 1934, shows a brake operator in which a pinion gear is moved by the lever over a stationary rack. A latch is provided to engage the pinion gear with the teeth of the stationary rack so as to prevent relative movement in the brake releasing direction of the pinion gear relative to the rack, holding the brake in the engaged position until such time as the latch is released to unlock the pinion gear.
U.S. Pat. No. 2,271,799--McCarthy, patented Feb. 3, 1942, discloses a rack and pinion brake actuator which is hand operated so that the parking brake is actuated when the hand lever is pulled. When the hand lever is pulled rearwardly from the housing, the rack is moved a distance regulated by the two pinion gears. The brake cable is attached to the rack so that it is tensioned by such movement of the rack. A clutch or pawl engages one of the pinion gears so as to lock both pinion gears against rotation, thus locking the rack in the brake applied position. The pawl is released by an actuating trigger mechanism which retracts the pawl tooth from engagement with the pinion gear, allowing release of the tension force in the brake cable which was keeping the parking brake applied, releasing the parking brake.
U.S. Pat. No. 2,672,061--Gardner, patented Mar. 16, 1954, also discloses a pinion gear and gear sector brake operator as well as a rack and pinion gear arrangement.
U.S. Pat. No. 3,403,581--Harness, patented Oct. 1, 1968, discloses a toothed rack and two toothed rotatable gears in meshing engagement with it. One of the gears is linearly movable toward and away from the other gear and therefore into and out of meshing engagement with the other gear to lock or release the mechanism. Such a mechanism could be applied to parking brake control mechanisms in which the brake cable is attached to the toothed rack which can be moved toward and from the cable tensioning direction, as shown in U.S. Pat. No. 2,271,799--McCarthy discussed above, 3,459,065--Fender discussed immediately below, or other similar rack and pinion gear arrangements also discussed herein.
U.S. Pat. No. 3,459,065--Fender, patented Aug. 5, 1969, has a pinion gear attached to a hand operated handle. A movable toothed rack engaged by the pinion gear has the brake operating cable attached to it. A toothed wheel on the pinion gear is selectively engaged and disengaged by a pawl. The pawl is biased into the engaged position by a spring and is disengaged by means of a pawl handle which is moved to move the pawl out of engagement with the wheel against the force of the biasing spring. U.S. Pat. No. 3,578,759--Yamazaki, patented May 18, 1971, has a somewhat different arrangement in that the brake is normally applied by depressing the foot operated lever which in turn pulls a cable to cause operation of the brake. A pawl engages a ratchet to hold the brake in the applied position. A rack on a hand operated shaft is engageable with a pinion gear to effect release of the brake when the handle is pushed forwardly.
U.S. Pat. No. 3,961,545--Petresh et al, patented Jun. 8, 1976, illustrates a rack and pinion parking brake actuator which is hand operated. The handle is attached to a toothed rack rod engaged by a pinion gear having a drum or pulley thereon to which the brake cable is attached. Movement of the rack rod causes rotation of the drum or pulley to apply tension to the brake cable. A spring clutch is provided to prevent movement of the drum to a release position until such time as the spring clutch is released by actuation of a release lever.
U.S. Pat. No. 4,793,206--Suzuki, patented Dec. 27, 1988, shows a cable strand attached to one end of a toothed rack which is engaged by a pawl to provide for elimination of excessive slack in the cable.
U.S. Pat. No. 4,850,242--Hass, issued Jul. 25, 1989, has a torsion clutch spring wound about a drum secured to and rotatable with a pedal lever so as to permit movement of the pedal lever to tension a parking brake cable attached to it, but to prevent movement of the pedal lever in the brake releasing direction so long as the clutch spring is in gripping relation with the drum. A pull handle is connected to the free end of the clutch spring which when pulled opens the clutch spring torsionally so that its grip on the drum is eliminated, allowing the pedal lever and the parking brake cable to return to the brake released position. It also discloses a second clutch spring arrangement that is activated when the brake cable is returned to the brake released position to activate a cable tension adjusting device which removes slack in the brake cable. Also, a push-to-release arrangement is shown which includes a toggle pawl and a spring device operable upon tapping of the pedal lever to place the system in a brake released condition.
U.S. Pat. No. 4,872,368--Porter, patented Oct. 10, 1989, has a pawl and ratchet mechanism for locking a parking brake operating mechanism in the brake cable tensioned, brake applied, position. An overcenter spring arrangement alternately pivotally biases the pawl in opposite directions to perform its locking and releasing functions. The pawl is alternately pivoted, first to the locking position when the pedal lever is moved from the released position toward a brake cable tensioning position for applying the parking brake. Once locked, further movement of the pedal lever in the cable tensioning direction causes release of the pawl from the ratchet. Then, alternatively, the pedal lever may be moved further in the cable tensioning direction to again lock the pawl to the ratchet as a higher cable tension force level, or the pedal lever may be released for return to the cable released or off position. Another alternative disclosed is the provision of a manually operable release rod for releasing the pawl from the bracket.
U.S. Pat. No. 4,949,592--Yamazaki et al, patented Aug. 21, 1990, includes a gear sector on a parking brake operating pedal lever, a pawl which is engaged with the gear sector so as to lock that sector against brake releasing movement, and a release linkage for releasing the pawl by operation of a release lever.
U.S. Pat. No. 5,138,899--Katagiri, patented Aug. 18, 1992, shows a pinion and gear sector arrangement wherein the gear sector is formed as part of the parking brake actuating arm. That gear sector is engaged by a pinion gear. The parking brake cable which is tensioned to apply the parking brake is connected to the brake actuating arm. Clutch springs prevent retrograde movement until such time as the release handle is pulled to effect release of the clutches and consequently the release of the parking brake.
U.S. Pat. No. 5,167,166--Ruhlman, patented Dec. 1, 1992, discloses another, later-patented, rack and pinion latching arrangement functionally similar to that of U.S. Pat. No. 3,403,581--Harness discussed above. The rack is connected to a cable. The arrangement is for the purpose of length adjustment, such as taking up excessive slack in the cable.
U.S. Pat. No. 5,170,867--Ojima et al, patented Dec. 15, 1992, shows the employment of torsion clutch springs in a parking brake operator lock and release mechanism, the springs being wound about drum surfaces.
U.S. Pat. No. 5,182,963--Perisho et al, patented Feb. 2, 1993, shows a parking brake pedal lever having a cable drum sector with a cam-shaped surface on the end opposite the pedal to which the parking brake cable is so connected that movement of the pedal lever in the brake applying direction will tension the cable. A gear sector is also on the pedal lever end opposite the pedal. The gear sector is in meshing engagement with a pinion gear which is secured to a clutch drum that is rotatably supported on the parking brake mechanism mounting bracket. A helical clutch spring is wound about and normally grips or releases the drum so as to prevent drum rotation in one direction but to permit drum rotation while the pedal lever is being moved in the brake applying direction. When preventing drum rotation after the pedal lever has been released so that the tension in the brake cable urges the pedal lever (and the drum acting through the pinion gear and gear sector) toward the brake released direction, the mechanism is latched or locked in the brake applied position. A hand operated rod may be moved to act through appropriate linkage to move the free end of the clutch spring so as to open up that spring, causing it to release the drum, and thus permitting brake releasing action of the mechanism.
U.S. Pat. No. 5,309,786--Pare et al, patented May 10, 1994, shows a parking brake actuator having a sector gear mounted on a mounting bracket so as to apply tension to a parking brake cable. A pedal lever is mounted on the mounting bracket for pivoting coaxially with the sector gear but independently of it. A spirally-wound spring extends between the lever and a drive plate for rotating the drive plate relative to the lever to apply an initial tension on the cable. A drive clutch couples the drive plate to the lever upon initial rotation of the lever out of brake release position to enable lever rotation to increasingly tension the brake cable and apply the parking brake. The drive clutch includes a pinion gear mounted on the pedal lever in engagement with the sector gear. A torsion clutch spring is wrapped about the pinion gear hub and has one end fixed to the lever. It has a free end, and normally contracts to prevent rotation of the pinion gear, thus operatively coupling the drive plate to the lever. A release pin on the mounting bracket is engaged by the torsion spring free end in the brake release position to expand the torsion clutch spring to free the pinion for rotation, thus decoupling the drive plate from the lever. Another control clutch has a torsion spring which releasably maintains the drive plate in the brake apply position.
U.S. Pat. No. 5,467,666--Soucie et al, filed Jul. 7, 1994, and patented Nov. 21, 1995, has a non-jamming self-adjust pawl and ratchet mechanism disclosed in an automotive parking brake system environment which is related to the present invention. When the pawl is engaged with the ratchet, it takes the tension load exerted by the tensioned brake cable and transmits it to the mounting bracket which is secured to a fixed part of the vehicle body. It is disclosed with three embodiments. In the first embodiment, the parking brake pedal lever is maintained in the brake-engaged position by a clutch spring and gear drum arrangement and the adjuster pawl is engaged with the ratchet for self-adjust. In the second embodiment, the parking brake pedal lever is maintained in the brake-engaged position by main pawl and main ratchet means, and the adjuster pawl and adjuster ratchet act as before. In the third embodiment, the operating lever is a hand lever that has the adjuster pawl and the main pawl pivotally mounted thereon. Each pawl is engageable with and disengageable from its own ratchet. The mechanism is not mounted in a pivoted housing.
U.S. Pat. No. 5,477,746--Perisho et al, filed Mar. 21, 1994, and patented Dec. 26, 1995, has a pair of cooperating lobe members providing a mechanical advantage between a parking brake operating lever and the parking brake cable. The lobes have cam surfaces connected by a flexible strap or belt that extends between the cooperating cam surfaces and is secured at opposite ends to the respective cams. A spring clutch and drum arrangement is associated with the drive lobe member for locking the lever in the brake applied position. Its free end is moved via a release cable to release the spring clutch's grip on the drum associated with the drive lobe member.
U.S. Pat. No. 5,485,762--Rothman, filed Jun. 20, 1994, and patented Jan. 23, 1996, relates to an adjuster to establish and maintain tension in a cable system. A linearly extending toothed rack ratchet member is engageable by two pawl members, both permitting passage of the ratchet member in the same direction.
Other background relates to the assembly of a parking brake mechanism so that it is in ready-to-ship condition to a vehicle assembly plant, and the installation of a parking brake operating mechanism in a vehicle. It is common practice to ship the parking brake control mechanism of which the hand or pedal lever is an integral part, the control release cable (if one is used) and the front brake cable separately to the assembly plant. Depending upon the sources of these components, they may even be, and often are, shipped from one to three different supplier manufacturing plants. This reduces shipping costs. Even when the conventional system is shipped as a preassembled unit, as is sometimes done, it requires a bulky package for shipping because of its shape as packaged. Of course, the advantage to pre-assembly and shipping as a unit is the reduction in assembly plant labor, which is often at a higher rate than is the labor in many supplier plants.
It is the most common practice to assemble the control and the front cable to each other in an off-line operation at the vehicle assembly plant when the parts noted above are separately shipped. This sub-assembly is then bolted into the vehicle, after which the front cable is threaded through the vehicle bodywork to meet and be attached to the rear brake cable. If a release cable is used, it is typically assembled to the vehicle instrument panel, then led to the parking brake operating mechanism to which it is then attached. The brake adjustment procedure then occurs. This procedure varies widely from one vehicle manufacturer to another, but still must be done.
It is also the usual practice to place a part of the operating lever in the brake tension force path with the parking brake operating mechanism locked in the parking brake applied position, thus keeping that lever, including its pivot, in the brake tension path for the entire period of time that the parking brake is applied, whether it be for hours, days, or even weeks. This requires that the operating lever be relatively bulky and strong, and made of a material to withstand such stress for long periods of time. Even when the operating lever is bypassed after locking, the mechanism does not use less hefty materials and structural elements than are otherwise used, and does not have the locking mechanism in a pivotally mounted housing to reduce side loads.